In-situ remedial cappingof

Sweden’s fiberbank sedimentsA unique challenge

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SAO Environmental Consulting AB

A unique challenge

Sweden’s sediment problem, in general2

• Bigger, more widespread than you may think• Both inland and coastal aquatic environments impacted• Different types of contaminated sediment

– Minerogenic (mineral-based)– Organic, i.e. fiberbank deposits and fiber-rich sediments

• Multiple organic, organometallic, and metallic contaminants• Numerous impacted sites or areas across the country• Numerous impacted sites or areas across the country

– Minerogenic sites/areas in at least 17 counties– Fiberbank sites/areas in at least 10 counties

• Risk assessments still being sorted out, but when completed, likely numerous sites will need some form of remediation

Reference: SGI / SAO, 2016 (Appendix A)

The solutions3

• Do nothing (often considered as a baseline)• Ex-situ and in-situ sediment remediation technologies available

– Ex-situ: based on removal, often dredging– In-situ: MNR, EMNR, capping, and capping-based treatment– Combinations

• Each has advantages and limitations• All are internationally recognized and accepted• All are internationally recognized and accepted• Each is proven-effective…..• IF and WHEN correctly chosen, designed, and implemented on a

project- and site-specific basis– No “one-size-fits-all” technology for all sites– Avoid a pre-conceived notion on what should be best for a site

Reference: SGI / SAO, 2016 (Appendix B)

The solutions: costs4

Dredging-based removal > in-situ capping >> MNR

Reference: SGI / SAO, 2016 (Appendix B)

Environmental goal: ”giftfri miljö”5

• Government’s definition– "Förekomsten av ämnen i miljön som har skapats i eller

utvunnits av samhället ska inte hota människors hälsa eller den biologiska mångfalden. Halterna av naturfrämmande ämnen är nära noll och deras påverkan på människors hälsa och ekosystemen är försumbar. på människors hälsa och ekosystemen är försumbar. Halterna av naturligt förekommande ämnen är nära bakgrundsnivåerna."

– Miljömålen ska vara nådda 2020. I dagsläget har samtliga län svarat att målet inte kommer att nås till 2020 med befintliga resurser.

• Some particularly relevant (but curious) parts

The reality (as I see it)

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”Halterna av naturfrämmande ämnen är nära noll …”

• Appropriate and realistic for future contaminant releases, but not for managing contaminated sediments already in place

• To meet this goal for already-deposited sediments would • To meet this goal for already-deposited sediments would require their near-total removal from aquatic environments

• Near-total removal not possible, economically or technically

A more realistic goal and approach7

” … och deras [ämnen] påverkan på människors hälsa och ekosystemen är försumbar”.

• This part of the ”giftfri miljö” definition is more realistic and practically doable (eventually)

• Recognize reducing risks associated with contaminatedsediments does not always require removal – far from itsediments does not always require removal – far from it

• Use available remediation (risk-reduction) technologies wisely– e.g. dredge where necessary, MNR or EMNR where possible

• Recognize in-situ capping comprises an especially diverse, flexible, and internationally proven set of remedies for adequately managing risks in a technically sound and cost-effective manner at a large number of sites

Need to act – soon8

”Miljömålen ska vara nådda 2020. … har samtliga län svarat att målet inte kommer att nås till 2020 med befintliga resurser”.

• So far, only a handful of contaminated sediment sites have been remediated in Sweden– 6 capping projects (3 minerogenic, 3 fiberbank)– 10 dredging projects (7 minerogenic, 3 fiberbank)– 10 dredging projects (7 minerogenic, 3 fiberbank)

• “Tip of the iceberg“• Contaminated sediments will not go away on their own

– Or will they? … The longer some sites remain un-remediated, the greater chance contamination will spread, causing larger and more-costly problems to deal with in the future

Reference: SGI / SAO, 2016 (Appendix C)

Need to act – soon9

• Doing nothing no longer an option, if it ever was• Cannot “un-ring the bell”• No, in-situ capping is not THE perfect or “miracle” solution

appropriate for all sites• Still, in-situ capping (in its various forms) can

– Offer adequate, cost-effective solutions at many sites– Offer adequate, cost-effective solutions at many sites– Be utilized to a much greater extent in Sweden than it

has been so far– Help make the most efficient use of available resources– Be an important remedial tool in helping to meet

realistic environmental goals – including meeting them sooner than later

In-situ capping: a brief overview10

Cappingcontaminated

sediments

Isolation Thin-layer Isolation capping

Conventional materials

Active materials

Thin-layer capping

Conventional materials

Activematerials

Reference: SGI / SAO, 2016 (main text)

A few main points11

• Isolation & thin-layer capping (two main strategies)• Each strategy has different cap performance

objectives, regardless of materials used• Conventional vs active materials (and capping)

– Applies to both capping strategies– Should consider conventional as “default”– When needed, active materials are more effective

or efficient in different ways

Isolation capping: conventional or active12

Cap performanceobjectives• Physical isolation of

benthic organisms from sediment

• Chemical isolation oforganisms in BAZ

new sediment biologically active zone (BAZ)

conventional active

organisms in BAZ from migratingcontaminants

• Protection ofsediment from erosion, dispersal

contaminated sediment

capsactivated carbon

not to scale

Thin-layer capping: conventional or active13

Cap performanceobjective• To significantly reduce,

but not necessarilyeliminate, organism exposure to and

conventional active

capsexposure to and bioaccumulation ofsediment contaminants

contaminated sediment

not to scale

• Conventional thin-layer capping (e.g. with sand) ≈ enhanced MNR• Active thin-layer capping (e.g. with AC) ≈ in-situ treatment

To meet cap performance objectives14

• Designed capping remedies must be consistent with site-specific conditions and sediment properties– Possible groundwater upwelling– Geotechnical stability of the capped sediment

• Sediment bearing capacity• Sediment bearing capacity• Slope stability

– Sediment-borne gases• Equipment/technique for cap construction is critical,

especially when capping soft sediments– And especially when not using geotextile support

ConventionalAnchor QEA

Anchor QEASAO

SAO

Conventional versus active materials

Active

NGIProf. D. Reible

AquaBlok, Ltd.

BioBlok Solutions AS

Cap construction: equipment & techniques

Prof. D. ReibleBioBlok Solutions AS BioBlok Solutions AS

AquaBlok, Ltd.

US ACEUS ACEUS ACE

BioBlok Solutions ASAquaBlok, Ltd.

AquaBlok, Ltd.AquaBlok, Ltd.

GPS positioning

benthic flux chamber

ROV camera

BioBlok Solutions ASBioBlok Solutions ASNGI

Cap monitoring: tools & techniques

Dr. J. Germano

Prof. U. Ghosh

BioBlok Solutions ASAquaBlok, Ltd.

SPIcamera

biologicalstudies

cores

Capping strategy, design, and materials18

• Most appropriate for each depends on many factors– Remedial (cap) performance objectives– Sediment contaminant(s)– Site conditions– Sediment characteristics– Construction equipment / placement technique– Construction equipment / placement technique– Site’s depositional vs erosional character– Concentration(s) and spatial extent of contamination– Rate and degree of risk reduction required– Costs– Etc.

• All are project- and site-specific decisions

Capping projects, worldwide 19

• Completed, initiated, planned (last few decades)• Pilot- or full-remedial scale

Location

Isolation capping projects Thin-layer capping projec ts

Conventional ActiveConventional

(EMNR)Active

(in-situ treatment)

• Capping is NOT new, novel, or un-tested

Internationally(includes all projects)

122 40 10 15

Norway 11 5 1 3

Sweden 5 0 1 0

Reference: SGI / SAO, 2016 (Appendix C)

BUT….. (a big but)

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• Basically all capping projects have involved contaminated minerogenic sediments

• Only three projects, worldwide, involved fiberbanksediments - and they have all been in Sweden!– Lake Turingen (conventional isolation, thin-layer)– Lake Turingen (conventional isolation, thin-layer)– Tollare (conventional isolation)

• Although very useful, the knowledge and experience gained from three projects does not constitute a convincing technology “track record”

A ”typical” fiberbank sediment site 21

Sources: SGU

The $64,000 question22

• Will capping approaches developed and refined for contaminated minerogenic sediments alsosuccessfully apply to capping fiberbank sediments?

They should….. theoretically23

• Minerogenic and fiberbank sediments are impacted by many of the same contaminants

• The same contaminant fate/transport processes are at play– Diffusion, advection, sorption, Hg methylation, etc.

• Fiberbank sediments are notoriously very soft, as are many minerogenic sediments

• Minerogenic sediments with very low shear strength can be successfully capped, often (but not always) without needing a basal geotextile for support– Again, proper cap construction is critical

And we have learned a few things from column-scale capping studies…..

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Karlshäll, LuleåColumn-scale capping studies

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General objectives• Demonstrate proof-of-concept for in-

situ isolation capping of Site sediments minus a geotextile component for basal support

gradual vs rapidcap placement

erosion-protection

layer(25 cm)

chemical-basal support

• Provide information for use in a follow-up pilot capping project

• Evaluate how fiberbank deposit versus fiber-rich sediments respond over time to placement and presence of a robust conventional isolation cap

chemical-isolation

layer(50 cm)

sediment(75 cm)

KarlshällColumn-scale capping studies

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Specific objectivesMonitor and evaluate sediment responses during and after capping• Over the short term (during → days)

– Sediment suspension– Cap and sediment mixing– Signs of bearing-capacity failure

• Over the longer term (weeks → months)– Signs of bearing-capacity failure– Sediment consolidation (rate, extent)– Sediment gases (formation, release)

KarlshällColumn-scale capping studies - results

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sediment suspensioncap/sediment mixing

gases

sedimentconsolidation

But the simple fact is all we really haveright now are questions

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• Is the real “problem customer” fiberbank deposits and not fiber-rich sediments?• Is gas a much bigger/longer-term issue, especially for fiberbank deposits?• Is Hg biogeochemistry more complicated in fiberbank sediments?• Will active capping be even more appropriate/necessary for fiberbank sediments?• Do fiberbank deposits have even lower shear strength than the softest/weakest

minerogenic sediments?• Will construction techniques for soft-sediment capping need to be modified?• How might the fibrous nature of fiberbank sediments affect their geotechnical

responses to cap loading?• What about capping sloped fiberbank deposits, especially if they are already

inherently unstable?• And what about how long-term land uplift could affect or influence a BUNCH of

stuff (erosion, stability, groundwater influences, biogeochemical processes, etc.)?

Reference: SGI / SAO, 2016 (Appendix D)

Path forward29

• Extensive research is needed to adequately answer such questions before full-scale remedial use of capping-based remedies for fiberbanksediments can be confidently recommended

• Field- scale pilot studies are a critical link between laboratory-scale work and full-scale remedial use

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Thanks for your attention ☺Thanks for your attention ☺